diff --git a/libs/evoral/src/Sequence.cpp b/libs/evoral/src/Sequence.cpp
index 0ca0537ac9..fb10bfac7b 100644
--- a/libs/evoral/src/Sequence.cpp
+++ b/libs/evoral/src/Sequence.cpp
@@ -880,11 +880,11 @@ Sequence<Time>::append_note_on_unlocked (NotePtr note, event_id_t evid)
         assert(_writing);
 
 	if (note->note() > 127) {
-		error << string_compose (_("illegal note number (%1) used in Note event - event will be ignored"), note->note()) << endmsg;
+		error << string_compose (_("illegal note number (%1) used in Note on event - event will be ignored"), (int)  note->note()) << endmsg;
 		return;
 	}
 	if (note->channel() >= 16) {
-		error << string_compose (_("illegal channel number (%1) used in Note event - event will be ignored"), note->channel()) << endmsg;
+		error << string_compose (_("illegal channel number (%1) used in Note on event - event will be ignored"), (int) note->channel()) << endmsg;
 		return;
 	}
 
@@ -915,9 +915,17 @@ Sequence<Time>::append_note_off_unlocked (NotePtr note)
         DEBUG_TRACE (DEBUG::Sequence, string_compose ("%1 c=%2 note %3 OFF @ %4 v=%5\n",
                                                       this, (int)note->channel(), 
                                                       (int)note->note(), note->time(), (int)note->velocity()));
-        assert(note->note() <= 127);
-        assert(note->channel() < 16);
         assert(_writing);
+
+	if (note->note() > 127) {
+		error << string_compose (_("illegal note number (%1) used in Note off event - event will be ignored"), (int) note->note()) << endmsg;
+		return;
+	}
+	if (note->channel() >= 16) {
+		error << string_compose (_("illegal channel number (%1) used in Note off event - event will be ignored"), (int) note->channel()) << endmsg;
+		return;
+	}
+
         _edited = true;
 
         if (_percussive) {